Are Sweet Potatoes or Yams Good for Blood Sugar?

by Sandi Busch

Yams are better for blood sugar than sweet potatoes.

Yams sold in the United States are actually a type of sweet potato. But technically, they're two different vegetables. Sweet potatoes originated in South America and are grown in the United States. True yams are native to Africa and are seldom sold in your local grocery store. The two potatoes also do not share similar carbohydrate profiles. As a result, sweet potatoes boost blood sugar, while yams help keep it balanced.

Impact on Blood Sugar

After you eat sweet potatoes and yams, their carbohydrates are digested into simple sugars that enter your bloodstream, causing a post-meal boost in blood sugar. For most people, this isn’t a problem because insulin escorts sugar into cells, which returns blood levels to normal. However, if you have health conditions that interfere with normal secretion or use of insulin -- insulin resistance, prediabetes or diabetes -- your body struggles to remove the extra sugar and blood levels remain high. Over time, high blood sugar may cause kidney disease and heart attacks, according to the Joslin Diabetes Center.

Glycemic Index Scores

The glycemic index rates carbohydrate-containing foods according to how much they affect blood sugar compared to glucose. Glycemic index scores are based on a scale of zero to 100, where 100 represents pure glucose. The scores are grouped into three categories: low, medium and high. A 150-gram serving of sweet potatoes, which is about the size of one typical potato, has a glycemic index score of 70. The score for the same portion of yams is 54, according to Harvard Health Publications. Yams are in the low category, so they’re good for blood sugar. Scores of 70 and above are high-glycemic foods, so sweet potatoes raise blood sugar.

Carbohydrate Content

If you only look at total carbohydrates you might think the glycemic scores are wrong. You’ll get 26.58 grams of total carbohydrates from a 150-gram serving of sweet potatoes. The same portion of yams has 41.22 grams of total carbohydrates. In spite of their higher carb content, yams have a smaller impact on blood sugar thanks to containing more fiber and less sugar. Sweet potatoes have 12 times more sugar and 3.8 grams of fiber, compared to 5.8 grams of fiber in yams. Soluble fiber slows down the rate of carbohydrate digestion, which helps prevent spikes in blood sugar.

Meal Planning Tips

If you eat a smaller serving of sweet potato, it will have less impact on blood sugar because you’ll get fewer total carbs and sugar. Eating three regular meals daily and including about the same amount of carbs at every meal also helps keep blood sugar balanced. The American Diabetes Association recommends getting about 45 to 60 grams of carbohydrates at each meal. Depending on your health and activity level, you may require a different amount, so talk to your health care provider to determine your optimal carbohydrate intake.

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About the Author

Sandi Busch has been a health writer since 2000. Her articles have been published in The Autism Asperger's Digest, The Pittsburgh Post-Gazette, newsletters for health organizations such as NAMI, the book "Early Intervention and Autism" and Web content for hospitals. Busch received her B.A. in psychology from Westminster College and studied nursing at George Mason University.

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